I've been using a rebel XSi and upgrading to a better camera. I've only been using the kit lens and thus I'm not stuck on a format just yet. I've been eyeing the D90 but I don't think I'd be happy with a kit lens, so I've been searching for a professional nikon lens and came across the following:

It's a 2.8 non-varying-with-zoom aperture which leads me to believe that it's comparable to a professional nikon. I know the build quality would be less, but what about image quality? What are your thoughts on this lens?

Also, is there a website that quantitatively compares lenses similar in nature how dxomark compares bodies? Thanks!

Well, from what I hear the variable aperture implies a lower quality lens. I see you own this lens, and you seem pleased with it. That's good to know. I'm basically wondering if I could get the d90 with a "professional" quality lens - without the price. I know, I'm asking a lot.

By professional - I mean something comparable to a Nikon lens that has the gold ring.

I would get the 18-105 for convenience because it is a really nice lens and a 50mm f1.8 AF-D for the professional feel!

Promaster ist a company startet with rebranding lenses in the 60s, I think, but I never heard of one today! They where never the brightest but solid quality lenses. I would take a new original Tamron 17-50 f2.8 instead if you want a fast zoom!